What octane is best, and why

[Dub11]

The more refined, premium fuels such as 91 and 92 octane seem to have a better shelf life than the lesser, cheaper cousins, and there is the ethanol issue with lower grade fuels. This is the primary reason why I run premium verses the other that usually give just a little more power. Chainsaws and other power equipment have a tendency to sit a long time with fuel in them. I've had chainsaws sit in my garage for 2+ years with BP premium start with no issues.

I use the same tactic.



The station I get my E free at also sells 102 at $8 a gallon. Seen a guy fill up his SSR with it bomb out of there like speed racer. I got a good chuckle

 

[Kiwioilboiler]

The more refined, premium fuels such as 91 and 92 octane seem to have a better shelf life than the lesser, cheaper cousins, and there is the ethanol issue with lower grade fuels. This is the primary reason why I run premium verses the other that usually give just a little more power. Chainsaws and other power equipment have a tendency to sit a long time with fuel in them. I've had chainsaws sit in my garage for 2+ years with BP premium start with no issues.

Could it be just that the Premium has more light ends to begin with Shaun, and so therefore even after a long enough period of time for some of those light ends to evaporate out, there are still enough to fire off the equipment?

 

[Hinerman]

The more refined, premium fuels such as 91 and 92 octane seem to have a better shelf life than the lesser, cheaper cousins, and there is the ethanol issue with lower grade fuels. This is the primary reason why I run premium verses the other that usually give just a little more power. Chainsaws and other power equipment have a tendency to sit a long time with fuel in them. I've had chainsaws sit in my garage for 2+ years with BP premium start with no issues.

Thanks. I will stick with 91 for the reasons you state. I do buy the 87 when we do some racing. I seriously doubt I could tell the difference in performance anyway.

 

[Bull Mountains]

It’s all about flame travel. When you introduce anti -knock compounds in gasoline it’s to slow down flame travel. It does that by making the flame “jump over” the molecules of anti-knock additive. When you have high octane fuel it means it literally takes longer to burn. That would be helpful in a high compression engine, preventing things like pre-ignition and detonation somewhat. Back to flame travel. The flame moves faster when the gas molecules are closer together. To slow the flame travel down you put stuff in it’s way. Lower octane has less stuff to get in the way, so the flame travels faster, producing more power in its allotted time in the cylinder. 87 non ethanol is the way to go.
There, octane 101.

High octane has little to no correlation with lower flame speed. Often the opposite is true.

 

[Bull Mountains]

Could it be just that the Premium has more light ends to begin with Shaun, and so therefore even after a long enough period of time for some of those light ends to evaporate out, there are still enough to fire off the equipment?

No, because the EPA dictates RVP parameters which limits the use of light ends.

 

[Bull Mountains]

Premium is the only way for me to get E-Free fuel. It also provides alittle insurance.

 

[av8or3]

High octane has little to no correlation with lower flame speed. Often the opposite is true.

Explain please

 

[Mastermind]

As messed up as an oil thread......

 

[jacob j.]

As messed up as an oil thread......

Would you expect it end up any other way?

 

[Mastermind]

Would you expect it end up any other way?

I suppose not.

 

[av8or3]

I thought my contribution was spot on. I’m waitin’
to hear how high octane has no correlation to flame travel.

 

[USMC615]

As messed up as an oil thread......

...and you thunk any different?

 

[Mastermind]

The Google weighs in.....

 

[av8or3]

https://www.hemmings.com/stories/20...-fiction-behind-those-higher-priced-fuels/amp

 

[foeke]

High octane is the only option without ethanol in it. All I need to know.
If it was the other way around, I would pick the low octane.
(Note, not living in the US)

 

[FederalQ]

Speaking of fuel shelf life, does anyone use the test kits available that have the giant “Q” tip and colorimetric chart to determine if the fuel is usable or not? I have used them on straight fuel but think it would not be helpful with dyed 2 cycle fuel.

 

[Lightning Performance]

So no one brought up oxygen supplements in the package additives.
Winter oxygenated fuel vs summer fuel?
Hell, does anyone even check on that, not likely.

What about deterrents or detergents?
You know... the cleaning additives.

Octane takes a third seat here for me. They sell that in bottles if needed. Old farm tractors run on 75 octane rated fuels but they only sell it new in stale as old-piss from third world countries or that eth *s-word degrading away in your fuel can right now. Put it back out in the sun to help it out some more

Shelf life is about three weeks on a modern summer package pump gas with eth from our local pumps if you keep it in a sealed container out of direct sunlight. Not shut, not covered but sealed up from air transfer to keep the water out and the light ends in. Piss poor fuel is the result if not used within weeks. Forgetabout months, troof.

The best octane is the fresh kind.

Back to your regularly scheduled flame front

 

[~WBF]

Explain please

I thought my contribution was spot on. I’m waitin’
to hear how high octane has no correlation to flame travel.

Here we go...haha

Fuel volatility level is set by Reid vaper pressure (RVP) which may be somewhere around 9 psi for 3 months in most of North America with a few exeptions such as CA for example. I believe (on memory) they are at 6.9 as a law and remain there year round. Summer fuel is more expensive to make as it's not a butane base but hold a bit more energy but runs like crap in cold weather. "Winter fuel" (which was once just called fuel) creates polution in the heat.
I've worked 12 winters in the Northwestern Canada and they can pump up the fuel volatility to 54 psi. Fuel up 4-5 ft away from a fire and spill a bit in the snow. The vapors travel under the snow and your jug and saw is on fire again. It's a lot of fun. I'm really good at extinguishing gas jugs and chainsaws but not really good at not catching them on fire. I think I've always liked it that way.

 

[Larry B]

Interesting thread. I am not a petrochemical engineer. I don't play one on TV and i didn't stay in a Holiday Inn Express last night. I don't have reasonable access to e free gas so i buy 87 octane 10% ethanol regular. I run a mower shop and i personally use about 75 gallons a year of fuel in mowers, small tractor and about a dozen 2 stroke hand helds. My Stihl FS80 is 20 years old and the only thing i have replaced is a split primer purge bulb. Always used regular pump gas in it. Just like everything else. I have a 361 clone and a 660 clone both running 200 psi compression and advenced timing. Regular ethanol gas and i run the piss out of them. No issues. My LawnBoy S21ZPM is about 30 years old and always used regular gas and have never had a carb issue. 2 strokes get dumped out and run dry in the off season and mowers get topped off and stored. I don't know what fuel is the "best" or "burns the hottest" or "cleanest". Just my personal experience for 30 years. Of course, i do make good money off people to lazy to drain the gas out of equipment for storage. If you run a mower shop ethanol is your friend.

 

[Bull Mountains]

Explain please

https://www.facebook.com/video.php?v=734686809901801

This might make it more clear to you.